<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title>粒子发射器</title>
    <style>
        canvas{
            display: block;
            margin: 10px auto;
            background-color: #000000;
        }
    </style>
</head>
<body>
<canvas id="cas" width="800" height="400"></canvas>

<script>
    var canvas = document.getElementById("cas");
    var ctx = canvas.getContext("2d");

    
</script>

</body>
</html>